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80 PCB007 MAGAZINE I DECEMBER 2018 ing Very Uniform and Ultrathin Copper by a Novel Catalyst System." This topic will explore a catalyst system that promotes very controlled copper thickness over the substrate targeting next-generation HDI to wafer-level packaging substrates. The paper discusses this new cat- alyst process, proposes a typical SAP process using the new catalyst, and demonstrates the reliability improvements through a compari- son between a new SAP PCB process and the conventional process. The second topic that will be presented is "Surface Treatment Enabling Low-Temperature Soldering to Aluminum." This surface treat- ment provides an alternative to anisotropic sil- ver pastes and is an easy-to-use stencil print- able. The presentation will discuss the process used to make functional aluminum circuits, study the resultant solder-aluminum bond, and shear results and reliability data. Dunn: Mike, there seems to be more and more discussion in the PCB market about SAP, modified SAP (mSAP), and substrate-like PCBs (SLPs). What is unique about Av- eratek's approach to SAP? Vinson: Averatek has a true semi- additive process enabling indus- try-leading sub-micron base cop- per thicknesses. These process- es also support the simultaneous formation of traces and vias. It is possible to omit electroless, and the process supports other metals such as gold and palladium for copperless applica- tions. Dunn: What factors do you see contributing to the drive to SAP technology? Vinson: I think that one of the primary things contributing to the drive to SAP technology is the feature-size limitations of subtractive tech- nology. Today's electronics push the envelope of what is possible, and more sophisticated electronics are driving the trace, space, and via sizes even smaller. SAP enables these finer fea- tures, can reduce layer count and the required lamination cycles, and allows a higher aspect ratio on traces and vias. Dunn: SAP in PCB manufacturing is an exciting topic. What do you see as the biggest challeng- es in SLP and SAP technology adoption? Vinson: I think this is a developing technology that is going to require the industry to reevalu- ate a number of things. From a designer's per- spective, there are no established design rules at this point; it takes a collaborative approach between design, fabrication, and assembly to achieve the required end product. From a fabri - cation perspective, I think fabricators will want to continue with their larger panel sizes, and there will be new equipment requirements as this technology is adopted. In general, the in- dustry is used to being able to have very short lead-times for very complex PCBs. Because this is an emerging technology oper- ating in a collaborative environ- ment, lead-times are going to be longer than some may be used to. Dunn: What advice do you have for designers and companies in- terested in exploring and imple- menting this technology? Vinson: One of the first pieces of advice I have is don't get hung up with the current design rules. Design rules are developing, and some of the rules for a sub- tractive etch process either are not applicable or will be significantly different than what we are used to. I would also like to mention that this technology does not have to be an all-or- nothing approach. It is possible to implement solutions with SAP being used on selective lay- ers and incorporated into a stackup that is also utilizing subtractive etch layers where these feature sizes are not required. This can result in a layer-count reduction and a more cost-ef- fective product. Dunn: Mike, you are working in somewhat un- charted waters for PCB fabrication. I am sure that can be both exciting and challenging. Mike Vinson

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